LSX ZEOLITHIC ZEOLITHIC ADSORBENTS WITH EXTERNAL SURFACE CONTROL, PREPARATION METHOD AND USES THEREO

专利摘要:
The present invention relates to a zeolitic adsorbent comprising at least one zeolite of structure FAU of type LSX and comprising barium and / or potassium, in which the external surface of said zeolite adsorbent, measured by nitrogen adsorption, is between 20 m 2. g-1 and 100 m2.g-1 terminals included. The present invention also relates to the use of such a zeolite adsorbent as an adsorbing agent, as well as the process for separating paraxylene from aromatic isomeric slices of 8 carbon atoms.
公开号:FR3028430A1
申请号:FR1460953
申请日:2014-11-13
公开日:2016-05-20
发明作者:Ludivine Bouvier；Cecile Lutz；Catherine Laroche；Julien Grandjean；Arnaud Baudot
申请人:IFP Energies Nouvelles IFPEN；Carbonisation et Charbons Actifs CECA SA；
IPC主号:

专利说明:

[0001] FIELD OF THE INVENTION [0001] The invention relates to zeolitic adsorbents in the form of agglomerates comprising zeolite with a structure of Faujasite (FAU). EXAMPLES OF EXTERNAL SURFACE-BASED ZEOLITE-BASED ZEOLITAN ADSORBENTS AND THEIR PREPARATION METHOD AND THEIR USES LSX-type for their use in applications where the transfer of material is an important parameter, said adsorbents having a controlled external surface, measured by nitrogen adsorption, of between 20 m2.g-1 and 100 m2.g-1. The present invention also relates to a process for preparing said zeolite adsorbents, and their uses, in particular for the separation of gaseous or liquid mixtures of isomers, more particularly xylenes and especially for the production of very pure paraxylene from an aromatic hydrocarbon feed containing isomers containing 8 carbon atoms. PRIOR ART The use of zeolitic adsorbents comprising at least zeolite Faujasite (FAU) type X or Y and comprising, in addition to sodium cations, barium, potassium or strontium ions, alone or in mixtures, for adsorbing selectively paraxylene in a mixture of aromatic hydrocarbons, is well known from the prior art. US Pat. Nos. 3,558,730, 3,558,732, 3,626,020 and 3,663,638 show that zeolitic adsorbents comprising aluminosilicates based on sodium and barium (US Pat. No. 3,960,774) or on sodium-based aluminosilicates. , barium and potassium, are effective for the separation of paraxylene present in aromatic C8 cuts (cuts comprising aromatic hydrocarbons with 8 carbon atoms). The adsorbents described in US Pat. No. 3,878,127 are used as adsorption agents in liquid phase processes, preferably of simulated countercurrent type, similar to those described in US Pat. No. 2,985,589 and which are incorporated herein by reference. apply, inter alia, to C8 aromatic cuts. US 6,884,918 recommends a faujasite X atomic Si / Al ratio between 1.15 and 1.5 exchanged with barium or barium and potassium. Document US 6,410,815 teaches that zeolite adsorbents as described in the prior art, but for which the faujasite is low in silica content and has an Si / Al atomic ratio close to 1 (that the LSX, an abbreviation for Low Silica X 3028430 - 2 - whose French translation is zeolite X with a low silica content), are advantageously used for the separation of paraxylene, especially when it is necessary to treat ethylbenzene-rich feedstocks as a result of a better selectivity of the paraxylene with respect to this isomer with respect to zeolite X adsorbents having an Si / Al atomic ratio between 1.15 and 1.5. In the patents listed above, the zeolitic adsorbents are in the form of crystals in the form of powder or in the form of agglomerates consisting mainly of zeolite powder and up to 20% by weight of inert binder. [0008] The synthesis of FAU zeolites is usually carried out by nucleation and crystallization of silico-aluminate gels. This synthesis leads to crystals (generally in the form of powder) whose use on an industrial scale is particularly difficult (significant losses of loads during handling). The agglomerated forms of these crystals in the form of grains, yarns and other agglomerates are preferred, these forms being obtainable by extrusion, pelletisation, atomization and other agglomeration techniques known to those skilled in the art. These agglomerates do not have the disadvantages inherent to the pulverulent materials. The agglomerates, whether they are in the form of platelets, beads, extrudates, and the like, generally consist of crystals of zeolite (s), which constitute the active element (in the sense of adsorption). ) and an agglomeration binder. This agglomeration binder is intended to ensure the cohesion of the crystals with each other in the agglomerated structure, but also to ensure sufficient mechanical strength to said agglomerates in order to avoid, or at least to minimize as much as possible, the risks of fractures, breakage or breakage which could occur during their industrial uses during which the agglomerates are subjected to numerous stresses, such as vibrations, strong and / or frequent variations in pressures, movements and the like. The preparation of these agglomerates is carried out for example by pasting zeolite crystals in powder form with a clay paste, in proportions of the order of 80% to 90% by weight of zeolite powder for 20% to 10% by weight of binder, then shaped into beads, platelets or extrudates, and high temperature heat treatment for clay firing and reactivation of the zeolite, the cationic exchange (s) (s) ), such as, for example, the barium and optionally potassium exchange that can be carried out before and / or after the zeolite powder has been agglomerated with the binder. We obtain zeolite agglomerates whose particle size is a few millimeters or even millimeter, and which, if the choice of agglomeration binder and granulation are made in the rules of the art, present a set of satisfactory properties, in particular porosity, mechanical strength, abrasion resistance. However, the adsorption properties of these agglomerates are obviously reduced relative to the starting active powder due to the presence of agglomeration binder inert with respect to the adsorption. Various means have already been proposed to overcome this disadvantage of the agglomeration binder to be inert with regard to the adsorption performance, among which is the conversion of all or at least part of the agglomeration binder. in active zeolite from the point of view of adsorption. This operation is now well known to those skilled in the art, for example under the name of "zeolitization". To carry out this operation easily, zeolitizable binders are used, most often belonging to the family of kaolinite, and preferably previously calcined at temperatures generally between 500 ° C. and 700 ° C. FR 2 925 366 discloses a process for the manufacture of zeolite LSX agglomerates with an Si / Al atomic ratio such as 1.00 Si / Al 1.15 exchanged with barium and optionally with barium and potassium, by agglomerating LSX zeolite crystals with a kaolinic binder, and then zeolizing the binder by immersing the agglomerate in an alkaline liquor. After exchanging the cations of the zeolite with barium (and optionally potassium) ions and activating, the agglomerates thus obtained have, from the point of view of the adsorption of the paraxylene contained in the C8 aromatic cuts and the mechanical strength, improved properties over adsorbents prepared from the same amount of LSX zeolite and binder, but the binder of which is not zeolite. In addition to a high adsorption capacity and good selectivity properties in favor of the species to be separated from the reaction mixture, the adsorbent must have good material transfer properties in order to guarantee a sufficient number of theoretical plates. to achieve effective separation of the mixed species, as Ruthven indicates in the book Principles of Adsorption and Adsorption Processes, John Wiley & Sons, ( 1984), pages 326 and 407. Ruthven indicates (ibid., Page 243) that in the case of an agglomerated adsorbent, the overall material transfer depends on the sum of the intracrystalline and intercrystalline diffusion resistances ( between the crystals). The intra-crystalline diffusional resistance is proportional to the square of the diameters of the crystals and inversely proportional to the intra-crystalline diffusivity of the molecules to be separated. The intercrystalline diffusion resistance (also called "macroporous resistance") is in turn proportional to the square of the diameters of the agglomerates, inversely proportional to the porosity contained in the macropores and mesopores (that is, that is, pores whose opening is greater than 2 nm) within the agglomerate, and inversely proportional to the diffusivity of the molecules to be separated in this porosity. The size of the agglomerates is an important parameter when using the adsorbent in the industrial application because it determines the pressure drop within the industrial unit and the uniformity of the filling. The particle size distribution of the agglomerates must therefore be narrow, and centered on number average diameters typically between 0.40 mm and 0.65 mm in order to avoid excessive pressure losses. The porosity contained in the macropores and mesopores within the agglomerate io (respectively inter-crystalline macroporosity and mesoporosity) can be increased by using porogenic agents, such as, for example, corn starch recommended in the US document. 8,283,274 to improve material transfer. However, this porosity does not participate in the adsorption capacity and the improvement of the transfer of macroporous material is then to the detriment of the adsorption capacity volume. Consequently, this pathway for improving the transfer of macroporous material is very limited. To estimate the improvement of the transfer kinetics, it is possible to use the plateau theory described by Ruthven in "Principles of Adsorption and Adsorption Processes", ibid., Pages 248-250. This approach is based on the representation of a column by a finite number of ideally stirred hypothetical reactors (theoretical stages). The equivalent height of theoretical plates is a direct measure of the axial dispersion and resistance to material transfer of the system. For a given zeolite structure, a given adsorbent size and a given operating temperature, the diffusivities are fixed, and one of the means for improving the transfer of material is to reduce the diameter of the crystals. A gain on the overall material transfer will thus be achieved by reducing the size of the crystals. The skilled person will therefore seek to reduce as much as possible the diameter of the zeolite crystals to improve the transfer of material. [0022] The patent CN 1,267,185C thus claims adsorbents containing 90% to 95% of BaX or BaKX zeolite for the separation of paraxylene, in which the zeolite X crystals are between 0.1 μm and 0 μm in size. , 4 pm and this in order to improve the material transfer performance. Similarly, the application US2009 / 0326308 describes a process for separating xylene isomers whose performance has been improved by the use of adsorbents based on zeolite X crystals less than 0.5 .mu.m in size. Patent FR 2 925 366 describes adsorbents containing LSX zeolite crystals with a number-average diameter of between 0.1 μm and 4.0 μm. The Applicant has nevertheless observed that the synthesis, filtration, handling and agglomeration of zeolite crystals whose size is less than 0.5 pm implement heavy, uneconomical processes and therefore difficult to industrialize. In addition, such adsorbents having crystals smaller than 0.5 μm, are also more fragile, and it then becomes necessary to increase the level of agglomeration binder in order to reinforce the cohesion of the crystals to each other within the adsorbent. However, the increase in the level of agglomeration binder leads to a densification of the adsorbents, which causes an increase in the macroporous diffusion resistance. Thus, despite reduced intra-crystalline diffusion resistance due to the decrease in the size of the crystals, the increase in the macroporous diffusional resistance due to the densification of the adsorbent, does not allow an improvement in the overall transfer. Moreover, the increase in the binder content does not make it possible to obtain a good adsorption capacity. [0025] There remains therefore a need for improved zeolite adsorbent materials prepared from LSX type FAU zeolite crystals which are easy to handle industrially, and of which said crystals (or constituent crystalline elements) are advantageously larger than 0 , 5 μm, and having improved overall material transfer over identical crystal size adsorbents known from the prior art, while maintaining adsorption capacity and adsorption selectivities of paraxylene vis-à-vis of its high isomers. These improved adsorbents would thus be particularly suitable for the separation of isomers xylenes gas phase or liquid phase. The present invention thus has for its first object to provide zeolitic adsorbents in the form of agglomerates with optimized properties for the separation of gaseous or liquid mixtures of isomers and more particularly for the separation of xylenes, in the gas phase or in liquid phase, especially paraxylene aromatic C8 cuts, and especially when said sections are rich in ethylbenzene. The zeolitic adsorbents of the invention advantageously have selectivity properties of para-xylene with respect to its isomers greater than 2.1, preferably greater than 2.3, and improved material transfer properties. while exhibiting high mechanical strength and adsorption capacity and are particularly suitable for use in a liquid phase paraxylene separation process, preferably of simulated countercurrent type. More specifically, the present invention relates to a zeolitic adsorbent comprising at least one zeolite of FAU structure of the LSX type and comprising barium and / or potassium, in which the outer surface of said zeolite adsorbent, measured by nitrogen adsorption, is between 20 m2.g-1 and 100 m2.g-1, limits included and more preferably between 20 m2.g-1 and 80 m2.g-1 limits included and even more preferably between 30 m2.g-1 and 80 m2.g-1, terminals included. It has indeed been found by the applicant that zeolite adsorbents with a controlled external surface area, that is to say between 20 m2.g-1 and 100 m2.g-1, as measured by adsorption. of nitrogen, and prepared from LSX zeolite crystals of Si / Al atomic ratio equal to 1.00 ± 0.05 having a size greater than 0.5 μm, exhibit improved overall material transfer over adsorbents. zeolites prepared from LSX zeolite crystals, of Si / Al atomic ratio and of identical size, but of external surface, measured by nitrogen adsorption, strictly less than 20 m 2 · g -1. The present invention therefore allows the provision of zeolitic adsorbents with improved properties over the prior art while facilitating the filtration, handling and agglomeration of zeolite powders used in the manufacturing process. Another object of the present invention is to provide a process for preparing said adsorbents, as well as the uses of said adsorbents for the separation of gaseous or liquid mixtures of isomers, more particularly xylenes and especially for the separation of very pure paraxylene from an aromatic hydrocarbon feed containing isomers containing 8 carbon atoms, and especially from a feed rich in ethylbenzene. Still another object of the present invention is to maximize the transfer of material within the zeolite adsorbent, while maintaining selectivities of paraxylene vis-à-vis its high isomers, especially greater than 2.1 and an adsorption capacity suitable for the application, together with a mechanical strength compatible with the application in question. DETAILED DESCRIPTION OF THE INVENTION Adsorbents according to the invention [0033] Thus, the present invention relates to a zeolitic adsorbent: comprising at least one zeolite of FAU structure of LSX type comprising barium and / or potassium, for which the external surface, measured by nitrogen adsorption, is between 20 m2.g-1 and 100 m2.g-1, and preferably between 20 m2.g-1 and 80 m2.g-1 and more preferably between between 30 and 80 m2.g-1 limits included. In one embodiment, the zeolite adsorbent of the invention has an Si / Al atomic ratio of between 1.00 and 1.50, preferably between 1.00 and 1.40 inclusive, more preferably between 1.00 and 1.20 inclusive, and even more preferably between 1.00 and 1.10 inclusive. In a preferred embodiment of the invention, the zeolite with structure FAU of the zeolite adsorbent is a zeolite of structure FAU of type LSX (generally defined by its atomic ratio Si / Al = 1.00 ± 0 , 05), for which the number average diameter of the crystals is between 0.5 μm and 20 μm, limits included, preferably between 0.5 μm and 10 μm, limits included, more preferably between 0.8 μm and 10 μm, inclusive, more preferably between 1 μm and 10 μm, inclusive, and more preferably between 1 μm and 8 μm inclusive. According to another preferred embodiment of the invention, the crystals have, together with the microporosity, internal cavities of nanometric size (mesoporosity), easily identifiable by observation by means of a Transmission Electron Microscope (TEM). or "TEM" in the English language) as described for example in US Pat. No. 7,785,563. The external surface of the zeolite adsorbent of the invention is calculated by the t-plot method from the isotherm of adsorption of nitrogen at a temperature of 77K, after vacuum degassing (P <6.7. 10-4 Pa), at a temperature between 300 ° C and 450 ° C for a period ranging from 9 hours to 16 hours, preferably at 400 ° C for 10 hours.  The outer surface of the FAU zeolite crystals of the adsorbent before agglomeration is measured in the same manner.  According to a preferred aspect, the barium content (Ba) of the zeolite adsorbent of the invention, expressed as barium oxide (BaO), is greater than 25%, preferably greater than 28%, so that very preferred greater than 34%, even more preferably greater than 37%, by weight relative to the total weight of the adsorbent, and advantageously, the barium content expressed as barium oxide (BaO) is between 28% and 42%, and typically between 37% and 40%, limits included, by weight relative to the total weight of the adsorbent.  According to another preferred aspect, the potassium content (K) of the zeolite adsorbent of the invention, expressed as potassium oxide (K 2 O), is less than 30%, preferably less than 15%, and preferred way between 0 and 10%, limits included by weight relative to the total weight of the adsorbent.  According to another preferred embodiment, the total content of alkaline or alkaline-earth ions, other than barium and potassium, expressed as total content of oxides of alkaline or alkaline-earth ions other than oxide. BaO barium and potassium oxide K2O, is between 0 and 5%, inclusive limits, relative to the total mass of the adsorbent.  Advantageously, the zeolitic adsorbent according to the invention has a total volume contained in the macropores and mesopores (sum of the macroporous volume and the mesoporous volume) measured by mercury intrusion, of between 0.15 cm 3. g-1 and 0.5 cm3. g-1, preferably between 0.20 cm3. g-1 and 0.40 cm3. g-1 and very preferably between 0.20 cm3. g-1 and 0.35 cm3. g-1, terminals included.  According to a preferred embodiment of the present invention, the zeolite adsorbent comprises at the same time macropores, mesopores and micropores.  By "macropores" are meant pores whose diameter is greater than 50 nm.  By "mesopores" is meant pores whose diameter is between 2 nm and 50 nm, limits included.  "Micropores" means pores whose diameter is less than 2 nm.  In addition, the adsorbent of the invention advantageously has a ratio (macroporous volume) / (macroporous volume + mesoporous volume) of between 0.2 and 1, very preferably between 0.5 and 0, 9, terminals included.  It is also preferred, in the context of the present invention, a zeolite adsorbent whose microporous volume, evaluated by the t-plot method from the nitrogen adsorption isotherm (N2) at a temperature of 25.degree. 77K, is greater than 0.160 cm3. g-1, preferably between 0.170 cm3. g-1 and 0.275 cm3. g-1 and more preferably between 0.180 cm3. g-1 and 0.250 cm3. g-1.  Said nitrogen adsorption isotherm is that also used for the measurement of the external surface by the t-plot method.  The crystalline structure of the LSX type FAU zeolite in the zeolite adsorbent of the present invention is identifiable by X-ray diffraction (known to those skilled in the art under the acronym DRX).  According to another preferred embodiment, no zeolite structure other than the FAU structure is detected by X-ray diffraction in the zeolite adsorbent of the present invention.  By "no zeolite structure other than the FAU structure" is meant less than 5%, preferably less than 2% by weight inclusive of one or more other zeolitic phases, other than the FAU structure. .  The mass fraction determined by XRD (technique described hereinafter) is expressed by weight relative to the total weight of the adsorbent.  The zeolitic adsorbent according to the invention also comprises, and preferably at least, a non-zeolitic phase which comprises, inter alia, an agglomeration binder used in the method of preparation to ensure the cohesion of the crystals with each other. where the term "agglomerated" or "zeolite agglomerate" sometimes used instead of the term "zeolite adsorbent" of the invention, as described above.  In the present invention, the term "binder" means an agglomeration binder which makes it possible to ensure the cohesion of the zeolite crystals (s) in the zeolite adsorbent (or agglomerated zeolite material) of the invention.  This binder is further distinguished from zeolite crystals in that it does not exhibit a crystalline structure, and in particular no zeolitic crystalline structure, for which reason the binder is often described as inert, and more precisely inert. with respect to adsorption and ion exchange.  According to a preferred embodiment, the mass fraction of zeolite FAU in the adsorbent is greater than or equal to 85%, preferably greater than or equal to 90% by weight, inclusive, relative to the total weight of the adsorbent of the present invention, the 100% complement being preferably constituted of non-zeolitic phase.  According to a particularly advantageous aspect, the mass fraction of zeolite FAU is between 92% and 98%, preferably between 94% and 98% by weight, limits included, relative to the total weight of the adsorbent of the present invention. the 100% complement is preferably non-zeolitic phase.  As already indicated, the mass fraction of zeolite (s) (crystallinity level) of the adsorbent according to the invention can be determined by X-ray diffraction analysis, known to those skilled in the art under the acronym XRD.  According to a preferred embodiment, the zeolitic adsorbent according to the invention has a loss on ignition, measured at 950 ° C. according to standard NF EN 196-2, between 3.0 and 7.7%, of more preferably between 3.5% and 6.7% and advantageously between 4.0% and 6%, limits included.  The zeolitic adsorbent according to the present invention exhibits, in particular, both mechanical strength, adsorption selectivities of paraxylene with respect to its isomers greater than 2.1, preferably greater than 2.2, more preferably greater than 2.3 and an adsorption capacity also very particularly suitable for use in the processes for separating xylene isomers in the gas phase or in the liquid phase.  In the context of the present invention, the mechanical strength is measured by the Shell method SMS1471-74 series adapted for agglomerates smaller than 1.6 mm.  This mechanical resistance, measured for the zeolite adsorbent defined above, is generally between 1.5 MPa and 4 MPa, preferably between 1.7 MPa and 4 MPa, more preferably between 1.8 MPa and 4 MPa and so preferably between 2 MPa and 4 MPa, inclusive.  Preparation of the adsorbents according to the invention Another object of the invention relates to a process for the preparation of the zeolite adsorbent such as has just been defined, said process comprising at least the steps of: a) agglomeration of crystals of at least one zeolite of structure FAU LSX type, 5 having an external surface of between 20 m2. g-1 and 150 m2. g-1, included terminals, preferably between 20 m2. g-1 and 120 m2. g-1, more preferably between 20 m2. g-1 and 100 m2. g-1, inclusive terminals, whose number average diameter of the crystals is between 0.5 μm and 20 μm, limits included, more preferably between 0.5 μm and 10 μm, limits included, more preferably between 0, 8 μm and 10 μm, inclusive, more preferably between 1 μm and 10 μm, limits included, and more preferably between 1 μm and 8 μm, inclusive, with a binder preferably comprising at least 80% clay or a mixture of clays and up to 5% of additives as well as with the amount of water which allows shaping of the agglomerated material, followed by drying and calcination of the agglomerates; B) optionally zeolizing step of all or part of the binder by contacting the agglomerates obtained in step a) with an aqueous basic solution; c) cationic exchange (s) of the agglomerates of step b) by contacting with a solution of barium ions and / or potassium ions; d) additional optional cation exchange of the agglomerates of step c) by contact with a solution of potassium ions; e) washing and drying the agglomerates obtained in steps c) or d), at a temperature between 50 ° C and 150 ° C; and f) obtaining the zeolite adsorbent according to the invention by activating the agglomerates obtained in step e) under oxidizing and / or inert gaseous flushing, with in particular gases such as oxygen, nitrogen, air, a dry air and / or decarbonated oxygen-depleted air, optionally dry and / or decarbonated, at a temperature between 100 ° C and 400 ° C, preferably between 200 ° C and 300 ° C.  In a preferred embodiment of the process for preparing the zeolite adsorbent of the present invention, the drying of the agglomerates in step a) above is generally carried out at a temperature of between 50.degree. C. and 150.degree. ° C, and the calcination of the dried agglomerates is generally carried out under oxidizing and / or inert gas scavenging, with in particular gases such as oxygen, nitrogen, air, dry and / or decarbonated air, depleted air oxygen, optionally dry and / or decarbonated, at a temperature above 150 ° C, typically between 180 ° C and 800 ° C, preferably between 200 ° C and 650 ° C, for a few hours, for example 2 hours at 6 o'clock.  In particular, said zeolite adsorbents are obtained from zeolite crystals having an external surface measured by nitrogen adsorption of between 20 m 2. g-1 and 150 m2. g-1, said zeolite crystals are preferably zeolite crystals with a hierarchical porosity.  By "zeolite with hierarchical porosity" is meant a zeolite possessing both micropores and mesopores, in other words a zeolite that is both microporous and mesoporous.  By "mesoporous zeolite" is meant a zeolite whose microporous zeolite crystals have, together with the microporosity, internal cavities of nanometric size (mesoporosity), easily identifiable by observation by means of a Transmission Electron Microscope (TEM). TEM "in English), as described for example in US 7,785,563.  According to a preferred embodiment, the crystals of said LSX-type FAU structure zeolite used in step a) have an Si / Al atomic ratio = 1.00 ± 0.05, measured by elemental chemical analysis, according to techniques well known to those skilled in the art and detailed below.  It is possible to prepare said zeolite crystals with an external surface of between 20 m 2. g-1 and 150 m2. g-1 by direct synthesis through the use of structuring agents or by seeding techniques and / or by adjustment of the synthetic operating conditions such as the SiO 2 / Al 2 O 3 ratio, the sodium content and the alkalinity synthesis mixture or by indirect synthesis according to post-treatment methods of conventional FAU zeolite crystals and known to those skilled in the art.  The post-treatment processes generally consist in removing atoms from the already formed zeolite network, either by one or more acid treatments which dealuminate the solid, treatment (s) followed by one or more washing (s) to sodium hydroxide (NaOH) in order to eliminate the aluminum residues formed, as described for example by D.  Verboekend et al.  (Adv.  Funct.  Mater. , 22, (2012), pp.  916-928), or else by treatments which combine the action of an acid and that of a structuring agent which improve the efficiency of the acid treatment, as described for example in application WO2013 / 106816.  The methods of direct synthesis of these zeolites (that is, synthetic methods other than post-treatment) are preferred and generally involve one or more structuring agents or sacrificial templates.  The sacrificial templates that can be used can be of any type known to those skilled in the art and in particular those described in application WO2007 / 043731.  According to a preferred embodiment, the sacrificial template is advantageously chosen from organosilanes and more preferably from [3- (trimethoxysilyl) propyl] -30-octadecyldimethylammonium chloride, [3- (trimethoxysilyl) propyl] chloride. hexadecyldimethylammonium chloride, [3- (trimethoxysilyl) propyl] dodecyldimethylammonium chloride, [3- (trimethoxysilyl) propyl] octylammonium chloride, N- [3- (trimethoxysilyl) propyl] aniline, 3- [2- ( 2-aminoethylamino) ethylamino] propyltrimethoxysilane, N- [3- (trimethoxysilyl) propyl] -N '- (4-vinylbenzyl) ethylenediamine, triethoxy-3- (2-imidazolin-1-yl) propylsilane , 1- [3- (trimethoxysilyl) propyl] urea, N- [3- (trimethoxysilyl) propyl] ethylenediamine, [3- (diethylamino) propyl] trimethoxysilane, (3-glycidyloxypropyl) trimethoxysilane, methacrylate, 3- (trimethoxysilyl) propyl, [2- (cyclohexenyl) ethyl] triethoxysilane, dodecyltriethoxysilane, hexadecyltri methoxysilane, (3-aminopropyl) trimethoxysilane, (3-mercaptopropyl) trimethoxysilane, (3-chloropropyl) trimethoxysilane, as well as mixtures of two or more of them in all proportions.  Of the sacrificial templates listed above, [3- (trimethoxysilyl) propyl] octadecyldimethylammonium chloride, or TPOAC, is particularly preferred.  It is also possible to use sacrificial templates having a higher molar mass and for example PPDAs (Polymer Poly-Diallyldimethylammonium), PVB (PolyVinyl Butyral) and other oligomeric compounds known in the art for increasing the diameter of the mesopores.  According to a preferred embodiment of the process of the present invention, in step a), the agglomeration of crystals of at least one zeolite FAU LSX type with hierarchical porosity is carried out, as previously described. prepared in the presence of a sacrificial template to be eliminated.  This elimination can be carried out according to the methods known to those skilled in the art, for example by calcination, and in a nonlimiting manner, the calcination of the zeolite crystals comprising the sacrificial template can be carried out under oxidizing gas scavenging and / or or inert, in particular with gases such as oxygen, nitrogen, air, dry air and / or decarbonated air, an oxygen-depleted air, optionally dry and / or decarbonated, at a temperature or temperatures above 150 ° C, typically between 180 ° C and 800 ° C, preferably between 200 ° C and 650 ° C, for a few hours, for example between 2 and 6 hours.  The nature of the gases, the ramps of temperature rise and the successive temperature levels, their durations will be adapted according to the nature of the sacrificial template.  The additional step of removing the eventual sacrificial template can be performed at any time during the process for preparing the zeolite adsorbent of the invention.  The elimination of said sacrificial template can thus advantageously be carried out by calcination of the zeolite crystals before the agglomeration step a), or else concomitantly with the calcination of the adsorbent during step a).  However, it is not beyond the scope of the invention if the agglomeration of step a) comprises the agglomeration of several LSX-type FAU zeolites having an Si / Al atomic ratio equal to 1, 00 ± 0.05 and having an external surface measured by nitrogen adsorption of between 20 m 2. g-1 and 150 m2. g-'obtained according to different modes.  The synthesis of zeolite FAU LSX type is generally in alkaline medium (sodium hydroxide and potassium and thus Na + and K + cations).  The LSX type FAU zeolite crystals thus obtained comprise mainly, or even exclusively, sodium and potassium cations.  However, it is not beyond the scope of the invention to use crystals which have undergone one or more cationic exchanges, between the synthesis before or after the possible elimination of the sacrificial template, if this step is carried out before the implementation of the procedure. step a).  In this case, step c) and possibly step d) of exchange may (possibly) not be necessary.  The size of the LSX type FAU zeolite crystals used in step a) and the FAU zeolite crystals in the adsorbents according to the invention are measured by scanning electron microscope (SEM) observation.  As indicated above, preferably, the number average diameter of the crystals is between 0.5 μm and 20 μm, inclusive, preferably between 0.5 μm and 10 μm, limits included, more preferably between 0.8. pm and 10 pm, inclusive, more preferably between 1 pm and 10 pm, inclusive, and more preferably between 1 pm and 8 pm, inclusive.  In this document, the term "number average diameter" or "size" is used, in particular for zeolite crystals.  The method of measuring these quantities is explained later in the description.  The agglomeration and the shaping of step a) can be carried out according to all the techniques known to those skilled in the art, and in particular according to one or more of the techniques chosen from extrusion, compacting, agglomeration on granulator plate, granulator drum, atomization and others.  The proportions of agglomeration binder (see definition below) and zeolite used are 8 parts to 15 parts by weight of binder for 92 parts to 85 parts by weight of zeolite.  At the end of step a) the finest agglomerated adsorbents can be removed by cycloning and / or sieving and / or oversize agglomerates by sieving or crushing, in the case of extrudates, for example .  The adsorbents thus obtained, whether in the form of beads, extrudates or the like, preferably have a volume average diameter, or their length (larger dimension when not spherical), between 0, 2 mm and 2 mm, and in particular between 0.2 mm and 0.8 mm and preferably between 0.40 mm and 0.65 mm, inclusive.  The binder that can be used in the context of the present invention may be chosen from conventional binders known to those skilled in the art, zeolitizable or non-zeolizable, and preferably chosen from clays and clay mixtures. silicas, aluminas, colloidal silicas, alumina gels, and the like, and mixtures thereof.  The clays are preferably chosen from: kaolin, kaolinite, nacrite, dickite, halloysite, attapulgite, sepiolite, montmorillonite, bentonite, illite and metakaolin, as well as mixtures of two or more of them in all proportions.  In step a), in addition to the zeolite crystal (s), the binder may also comprise one or more additives.  The additives are preferably organic, for example lignin, starch, carboxymethylcellulose, surfactant molecules (cationic, anionic, nonionic or amphoteric), intended to facilitate the handling of the zeolite / clay paste ( s) by modifying the rheology and / or stickiness or to give the final adsorbents satisfactory properties, in particular macroporosity.  Mention may preferably be made of, but not limited to, methylcelluloses and their derivatives, lignosulfonates, polycarboxylic acids and carboxylic acid copolymer acids, their amino derivatives and their salts, in particular alkaline salts and ammonium salts. .  The additives are introduced at 0 to 5%, preferably from 0.1 to 2%, by weight based on the total weight of the adsorbent.  The additives may also comprise a source of liquid and / or solid silica, preferably representing from 1% to 5% of the total mass of said solids.  The possible source of silica may be of any type known to those skilled in the art, specializing in the synthesis of zeolites, for example colloidal silica, diatoms, perlite, calcination ash ("fly ash" English language), sand, or any other form of solid silica.  For the calcination included in step a), the nature of the gases, the ramps for temperature rise and the successive temperature increments, as well as their respective durations, will be adapted in particular according to the nature of the sacrificial template to be eliminated and depending on the nature of the binder used in the agglomeration step a).  The SEM observation of the zeolitic adsorbent makes it possible to confirm the presence of non-zeolitic phase comprising, for example, agglomeration binder or any other amorphous phase in the adsorbents.  The cationic exchange (s) (s) (c) and (d) stages described above are carried out according to the conventional methods known to those skilled in the art, and most often by contacting the adsorbents of step a) or of step b) with a barium salt, such as barium chloride (BaCl 2) and / or potassium (KCl) and / or barium and potassium, in aqueous solution at a temperature between room temperature and 100 ° C, and preferably between 80 ° C and 100 ° C to quickly obtain high levels of barium, i. e.  levels preferably of greater than 25%, preferably greater than 28%, very preferably greater than 34%, even more preferably greater than 37%, expressed by weight of barium oxide relative to the total mass. adsorbent.  Advantageously, the barium content expressed as barium oxide is between 28% and 42%, and typically between 37% and 40%, limits included, by weight relative to the total weight of the adsorbent.  It is preferred to operate with a large excess of barium ions relative to the cations of the zeolite that it is desired to exchange, typically an excess of the order of 10 to 12, advantageously by proceeding by successive exchanges.  Potential exchange with potassium in step d) can be performed before and / or after the barium exchange (step c).  It is also possible to agglomerate in step a) / 5 LSX-type zeolite crystals already containing barium or potassium ions or barium and potassium (pre-exchange of the cations present in the zeolite LSX type starting, typically sodium and potassium cations by barium or potassium ions or barium and potassium before step a) and overcome (or not) steps c) and / or d).  Surprisingly, the Applicant has observed that the cationic zo exchange step, which can be delicate because of the relative fragility of the zeolite crystal structure with hierarchical porosity, does not affect the intrinsic properties of the surface. external and microporous volume (returned to the mass of the adsorbent once exchanged) said zeolite crystals with hierarchical porosity.  After the cationic exchange step (s), the mixture is then washed, generally and preferably with water, followed by drying of the adsorbent thus obtained. (step e).  The activation which follows the drying (step f) is carried out in a conventional manner, according to the methods known to those skilled in the art, for example at a temperature generally between 100 ° C. and 400 ° C., as indicated previously in step f) of the process.  The activation is carried out for a period of time as a function of the desired loss on ignition.  This duration is generally between a few minutes and a few hours, typically between 1 hour and 6 hours.  The present invention also relates to the uses of the zeolite adsorbents described above as adsorption agents which may advantageously replace the adsorbents described in the literature, based on crystals. Conventional zeolite FAU LSX type, comprising barium and / or potassium, and in particular in the uses listed below: separation of cuts of aromatic isomers C8 and in particular xylenes, separation of isomers of substituted toluene such as nitrotoluene, diethyltoluene, toluenediamine, and others; separation of cresols; separation of polyhydric alcohols, such as sugars.  According to another object, the present invention relates to a process for separating the isomers of xylenes in the gas phase or in the liquid phase using at least one zeolite adsorbent as defined above, and preferably in which the zeolite crystals (s) Zeolitic adsorbent are prepared by direct synthesis using one or more structuring agents (or sacrificial templates).  The invention relates in particular to a process for separating paraxylene from a filler of cuts of aromatic isomers with 8 carbon atoms, using, as paraxylene adsorption agent, a zeolite adsorbent as defined above. , and in particular a zeolite adsorbent based on FAU LSX type comprising barium and / or potassium and having a large external surface characterized by nitrogen adsorption, typically between 20 m 2. g-1 and 100 m2. g-1, and more preferably between 20 m2. g-1 and 80 m2. g-1 and even more preferably between 30 and 80 m2. g-1 limits included, implemented in liquid phase processes, but also in gaseous phase.  The separation process according to the invention can be carried out by preparative adsorption liquid chromatography (batch), and advantageously continuously in a simulated moving bed unit, that is to say against simulated current or simulated co-current, and more particularly counter-current simulated.  The operating conditions of an industrial adsorption unit in simulated moving bed, operating against the current, are in general the following: - number of beds: 4 to 24; number of zones: at least 4 operating zones, each located between a feed point (feed flow to be treated or desorbent flow) and a withdrawal point (raffinate flow or extract flow); advantageously at a temperature of between 100 ° C. and 250 ° C., preferably between 140 ° C. and 190 ° C .; pressure between the bubble pressure of xylenes (or toluene when toluene is chosen as the desorbent) at the process temperature and 3 MPa; The ratio of desorbent flows on charge: 0.7 to 2.5, preferably 0.7 to 2.0 (for example 0.9 to 1.8 for a single adsorption unit ("stand alone"); In the English language) and 0.7 to 1.4 for an adsorption unit combined with a crystallization unit); 5 - recycling rate: 2 to 12, preferably 2.5 to 6; - Cycle time, corresponding to the time between two injections of desorbent on a given bed: advantageously between 4 and 25 min.  [0091] Reference may also be made to the teaching of US Pat. Nos. 2,985,589, 5,284,992 and 5,629,467.  The operating conditions of a simulated co-current adsorption industrial unit are generally the same as those operating at simulated counter-current with the exception of the recycling rate, which is generally between 0.degree. 8 and 7.  We can refer to the patents US4402832 and US4498991.  The desorbent is a desorption solvent whose boiling point is less than that of the feed, such as toluene or greater than that of the feedstock, such as para-diethylbenzene (PDEB).  Advantageously, the desorbent is toluene or paradiethylbenzene.  The selectivity of the adsorbents according to the invention for the adsorption of paraxylene contained in C8 aromatic cuts is optimal when their loss on ignition zo measured at 950 ° C. is preferably less than or equal to 7.7%, of preferably between 0 and 7.7%, very preferably between 3.0% and 7.7%, more preferably between 3.5% and 6.5% and even more preferably between 4.5%. and 6%, limits included.  The water content in the incoming streams is preferably adjusted between 20 ppm and 150 ppm, for example by adding water to the feed and / or desorbent streams.  In addition, it has been noted that the selection of an outer surface greater than 20 m2. g-1 as previously indicated makes it possible to reduce the transport time to the micropores, leading to a significantly improved material transfer compared to the prior art.  Moreover, it has been noticed that the selection of an external surface of between 20 m2. g-1 and 100 m2. g-1, as indicated above, associated with the choice of an LSX-type FAU zeolite with an Si / Al atomic ratio equal to 1.00 ± 0.05 makes it possible to obtain adsorption selectivities for paraxylene with respect to other isomers sufficient for good separation, and especially paraxylene selectivities to ethylbenzene, which have the highest affinity for the adsorbent after paraxylene, greater than 2.1. .  It has been noted that the selectivity of paraxylene with respect to ethylbenzene of LSX based adsorbents with the same Si / Al atomic ratio whose external surface area is greater than 100 m 2. g-1 or adsorbents based on zeolite type FAU X Si / Al atomic ratio greater than 1.00 ± 0.05 and outer surface of between 20 m2. g-1 and 100 m2. g-1, is strictly less than 2.1.  Another advantage is that crystals of micrometric size (typically between 0.5 μm and 20 μm, inclusive) can be provided, preferably between 0.5 μm and 10 μm, limits included, more preferably between 0.8 μm and 10 μm, limits included, more preferably between 1 μm and 10 μm, limits included, and more preferably between 1 μm and 8 μm, limits included) which are more easily manipulated, thus making the production of adsorbents easier.  [0099] Thus, the zeolitic adsorbents of the invention have, in particular, improved material transfer properties while maintaining optimum selectivity properties of paraxylene with respect to its isomers, and typically greater than 2.1, and that of adsorption capacity, and maintaining a high mechanical strength for use in a method of separation of paraxylene in the liquid phase, preferably simulated countercurrent type.
[0002] CHARACTERIZATION TECHNIQUES Granulometry of zeolitic crystals - Detection of mesopores [0100] The estimation of the average number diameter of the zeolite crystals FAU used during agglomeration (step a) and the crystals contained in the zeolitic adsorbents according to the invention is performed by observation by scanning electron microscope (SEM). In order to estimate the size of the zeolite crystals on the samples, a set of images is carried out at a magnification of at least 5000. The diameter of at least 200 crystals is then measured using a dedicated software. The accuracy is of the order of 3%. As indicated in US Pat. No. 7,785,563, the transmission electron microscope (TEM) further makes it possible to verify whether the zeolite crystals of the adsorbent of the present invention are solid (ie non-mesoporous) zeolite crystals or aggregates of solid zeolite crystals or mesoporous crystals (compare the MET images of Figure 1, where the mesoporosity is clearly visible and Figure 2 shows solid crystals). The MET observation thus makes it possible to visualize the presence or absence of the mesopores. Chemical analysis of zeolitic adsorbents - Si / Al ratio and exchange rate: A basic chemical analysis of the final product obtained at the end of steps a) to f) described above, can be carried out according to different analytical techniques known to those skilled in the art. Among these techniques, mention may be made of the X-ray fluorescence chemical analysis technique as described in standard NF EN ISO 12677: 2011 on a wavelength dispersive spectrometer (VVDXRF), for example Tiger S8 from the Bruker company. [0104] X-ray fluorescence is a non-destructive spectral technique exploiting the photoluminescence of atoms in the X-ray domain, to establish the elemental composition of a sample. The excitation of the atoms generally by an X-ray beam or by bombardment with electrons, generates specific radiations after return to the ground state of the atom. The X-ray fluorescence spectrum has the advantage of relying very little on the chemical combination of the element, which offers a precise determination, both quantitative and qualitative. A measurement uncertainty of less than 0.4% by weight is obtained conventionally after calibration for each oxide. These elementary chemical analyzes make it possible both to check the Si / Al atomic ratio of the zeolite used during the preparation of the adsorbent, as well as the Si / Al atomic ratio of the adsorbent, and to verify the quality of the the ion exchange described in step c) and in optional step d). In the description of the present invention, the measurement uncertainty of the Si / Al atomic ratio is ± 5%. The quality of the ion exchange is related to the number of moles of sodium oxide, Na 2 O, remaining in the zeolite adsorbent after exchange. For example, the exchange rate by barium ions is estimated by evaluating the ratio between the number of 25 moles of barium oxide, BaO, and the number of moles of the whole (BaO + Na2O + K2O). Similarly, the exchange rate by potassium ions is estimated by evaluating the ratio between the number of moles of potassium oxide K2O and the number of moles of the whole (BaO + K2O + Na2O). It should be noted that the contents of various oxides are given in percentage by weight relative to the total weight of the anhydrous zeolite adsorbent. Granulometry of zeolite adsorbents: The determination of the average volume diameter of the zeolite adsorbents obtained at the end of step a) of agglomeration and shaping is carried out by analysis of the particle size distribution of a sample of image adsorbent according to ISO 13322-2: 2006, using a treadmill allowing the sample to pass in front of the camera lens. The volume mean diameter is then calculated from the particle size distribution by applying the ISO 9276-2: 2001 standard. In this document, the term "volume mean diameter" or "size" is used for zeolite adsorbents. The accuracy is of the order of 0.01 mm for the adsorbent size range of the invention. Mechanical resistance of zeolite adsorbents: The crush resistance of a bed of zeolitic adsorbents as described in the present invention is characterized according to the Shell method SMS1471-74 series (Shell Method Series SMS1471-74 "Determination of Bulk Crushing Strength of Catalysts, Compression-Sieve Method, associated with the BCS Tester device marketed by Vinci Technologies. This method, initially intended for the characterization of catalysts from 3 mm to 6 mm is based on the use of a sieve of 425 pm which will allow in particular to separate the fines created during the crash. The use of a 425 μm sieve remains suitable for particles of diameter greater than 1.6 mm, but must be adapted according to the particle size of the adsorbents that are to be characterized. The adsorbents of the present invention, generally in the form of beads or extrudates, generally have a mean diameter by volume or a length, ie the largest dimension in the case of non-spherical adsorbents, of between 0.2 mm. and 2 mm, and in particular between 0.2 mm and 0.8 mm and preferably between 0.40 mm and 0.65 mm inclusive. Therefore, a 100 μm sieve is used in place of the 425 μm sieve mentioned in the standard Shell method SMS1471-74. The measurement protocol is as follows: a 20 cm.sup.3 sample of agglomerated adsorbents, previously sieved with the appropriate sieve (100 .mu.m) and previously dried in an oven for at least 2 hours at 250.degree. instead of 300 ° C mentioned in the standard Shell method SMS1471-74), is placed in a metal cylinder of known internal section. An increasing force is imposed in stages on this sample by means of a piston, through a bed of 5 cm3 of steel balls in order to better distribute the force exerted by the piston on the agglomerated adsorbents (use of 2 mm diameter for particles of spherical shape of diameter strictly less than 1.6 mm). The fines obtained at the different pressure levels are separated by sieving (100 μm sieve) and weighed. The crush strength in bed is determined by the pressure in megaPascal (MPa) for which the amount of cumulative fines passing through the sieve amounts to 0.5% by weight of the sample. This value is obtained by plotting the mass of fines obtained as a function of the force applied to the adsorbent bed and by interpolating at 0.5% by mass of cumulated fines. The mechanical resistance to crushing in a bed is typically between a few hundred kPa and a few tens of MPa and generally between 0.3 MPa and 3.2 MPa. The accuracy is conventionally less than 0.1 MPa.
[0003] Identification and quantification of zeolite fractions of zeolite adsorbents and estimation of the mesh parameter The identification of the zeolite fractions contained in the adsorbent is carried out by X-ray diffraction analysis (XRD). This analysis is carried out on a device of the Bruker brand. The identification of the crystalline phases present in the zeolite adsorbent is carried out by comparison with the sheets of the ICDD database and possibly by comparison with the diffractogram of an appropriate reference (LSX type FAU zeolite crystals (presumed to be 100% crystalline) Si / Al atomic ratio equal to 1.00, and having undergone the same cation exchange treatments as the adsorbent considered). For example, the presence of the X / 5 zeolite exchanged with Barium will be confirmed by comparing the lines of the diffractogram obtained with the ICDD sheet No. 38-0234 ("Zeolite X, (Ba)"). The comparison of the diffractograms is completed by a comparison of the mesh parameters measured on the reference zeolite and on the adsorbent under consideration. The measurement of the zeolite mesh parameter is performed accurately (to ± 0.01 Â): to do this, an internal zo standard (NIST-certified Si 640b) is added and the data is processed with the TOPAS refinement software. . For example, a measurement carried out on zeolite X crystals having a Si / Al atomic ratio of 1.25 and exchanged at 95% by barium gives a mesh parameter of 25.02 ± 0.01 Å, while A measurement made on LSX zeolite crystals with a Si / Al atomic ratio of 1.00 and exchanged at 95% by barium gives a mesh parameter of 25.19 ± 0.01 Å. The amount of the zeolite fractions is evaluated from the relative peak intensities of the diffractograms by taking as reference the peak intensities of the reference zeolite mentioned above. The peaks, making it possible to go back to crystallinity, are the most intense peaks of the angular zone between 9 ° and 37 °, namely the peaks observed in the angular ranges of between 11 ° and 13 °, respectively, between 22 ° and 26 ° and between 31 ° and 33 °. Microporous Volume and External Surface The crystallinity of the zeolite adsorbents of the invention is also evaluated by measuring their microporous volume by comparing it with that of a suitable reference (100% crystalline zeolite under identical cationic treatment conditions or theoretical zeolite). This microporous volume is determined from the measurement of the gas adsorption isotherm, such as nitrogen, at its liquefaction temperature. Prior to the adsorption, the zeolitic adsorbent is degassed between 300 ° C and 450 ° C for a period of between 9 hours and 16 hours under vacuum (P <6.7 × 10 -4 Pa). The measurement of the nitrogen adsorption isotherm at 77K is then carried out on an ASAP 2020 M type apparatus of Micromeritics, taking at least 35 measurement points at relative pressures with a P / Po ratio of between 0.002 and 1. The microporous volume and the external surface are determined by the t-plot method from the obtained isotherm, by applying the ISO 15901-3: 2007 standard and by calculating the statistical thickness t by the Harkins-Jura equation. The microporous volume and the external surface are obtained by linear regression on the points of the t-plot between 0.45 nm and 0.57 nm, respectively from the ordinate at the origin and the slope of the linear regression. . The microporous volume evaluated is expressed in cm 3 of liquid adsorbate per gram of anhydrous adsorbent. The external surface is expressed in m2 per gram of anhydrous adsorbent. Macroporous and Mesoporous Volume and Grain Density Macroporous and mesoporous volumes as well as grain density are measured by mercury intrusion porosimetry. An Autopore® 9500 mercury porosimeter of Micromeritics is used to analyze the distribution of the pore volume contained in the macropores and in the mesopores. The experimental method, described in the operating manual of the apparatus referring to the ASTM D4284-83 standard, consists of placing a sample of adsorbent (zeolite granular material to be measured) (known fire loss) previously weighed. in a cell of the porosimeter, then, after a prior degassing (discharge pressure of 30 pm Hg for at least 10 min), to fill the cell with mercury at a given pressure (0.0036 MPa), and then to apply increasing pressure stepwise up to 400 MPa in order to gradually penetrate the mercury into the porous network of the sample. The relationship between the applied pressure and the apparent pore diameter is established assuming cylindrical pores, a mercury-pore wall contact angle of 140 ° and a mercury surface tension of 485 dynes. cm. The cumulative amount of mercury introduced as a function of the applied pressure is recorded. The value at which the mercury fills all the inter-granular voids is fixed at 0.2 MPa, and it is considered that, beyond this, the mercury penetrates the pores of the granular material. The volume of grain (Vg) is then calculated by subtracting the cumulative volume of mercury at this pressure (0.2 MPa) from the volume of the cell of the porosimeter, and dividing this difference by the mass of the equivalent granular material. anhydrous, that is to say the mass of said material corrected for loss on ignition. The grain density is the inverse of the grain volume (Vg), and is expressed in grams of anhydrous adsorbent per cm3. The macroporous volume of the granular material is defined as the accumulated volume of mercury introduced at a pressure of between 0.2 MPa and 30 MPa, corresponding to the volume contained in the pores with an apparent diameter greater than 50 nm. The mesoporous volume of the granular material is defined as the cumulative volume of mercury introduced at a pressure of between 30 MPa and 400 MPa. In this document, the macroporous and mesoporous volumes of the zeolite adsorbents, expressed in cm3.g-1, are thus measured by mercury intrusion and reported to the mass of the sample in anhydrous equivalents, that is, that is, the mass of said material corrected for loss on ignition. Loss on ignition of zeolite adsorbents: The loss on ignition is determined in an oxidizing atmosphere, by calcination of the sample in air at a temperature of 950 ° C. ± 25 ° C., as described in standard NF EN 196-2 (April 2006). The standard deviation of measurement is less than 0.1%. Characterization of liquid phase adsorption by drilling: The technique used to characterize the adsorption of molecules in the liquid phase on a porous solid is the so-called drilling technique described by Ruthven in "Principles of Adsorption and Adsorption Processes". "(Chapters 8 and 9, John Wiley & Sons, 1984) which defines the technique of breakthrough curves as the study of the response to the injection of a step of adsorbable constituents. The analysis of the average time of exit (first moment) of the drilling curves provides information on the adsorbed quantities and also makes it possible to evaluate the selectivities, that is to say the separation factor, between two adsorbable constituents. The injection of a non-adsorbable component used as a tracer is recommended for the estimation of non-selective volumes. Analysis of the dispersion (second moment) of the drilling curves makes it possible to evaluate the equivalent height of theoretical plates, based on the representation of a column by a finite number of ideally stirred hypothetical reactors (theoretical stages), which is a direct measurement of the axial dispersion and resistance to material transfer of the system. EXAMPLES Example A Synthesis of Conventional LSX Zeolite Crystals (Synthesis A of Patent FR 2 925 366) (Comparative Example) Crystals are prepared according to Synthesis A described in Patent FR 2925366). The crystals obtained after filtration, washing and drying are identified by X-ray diffraction as faujasite. Chemical analysis of the solid gives a ratio Si / Al = 1.01. The microporous volume and the external surface measured by the t-plot method from the nitrogen adsorption isotherm at 77K after vacuum degassing at 400 ° C. for 10 hours are respectively 0.305 cm 3 / g and 6 m2 / g. The analysis of the size of the zeolite crystals is carried out by scanning electron microscopy. The average crystal size is 2.6 μm. Example B: Synthesis of zeolite crystals FAU with hierarchical porosity Example B1: Synthesis of zeolite crystals of XPH type with Si / Al ratio = 1.24 of external surface equal to 90 m 2 g -1 (comparative example) [0129 A zeolite X with an external surface equal to 90 m 2 g -1 is synthesized directly according to the synthesis mode described in the article Inayat et al. (Angew Chem Int.Ed., (2012), 51, 1962-1965).
[0004] Step 1): Preparation of the growth gel in stirred reactor with Archimedes screw at 300 rpm. In a stainless steel reactor equipped with a heating jacket, a temperature probe and a stirrer, a growth gel is prepared by mixing an aluminate solution containing 119 g of sodium hydroxide (NaOH ) at 128 g of alumina trihydrate (Al 2 O 3, 3H 2 O, containing 65.2% by weight of Al 2 O 3) and 195.5 g of water at 25 ° C. in 25 minutes with a stirring speed of 300 rpm -1 in a silicate solution containing 565.3 g of sodium silicate, 55.3 g of NaOH and 1997.5 g of water at 25 ° C. The stoichiometry of the growth gel is as follows: 3.48 Na 2 O / Al 2 O 3 / 3.07 SiO 2/180 H 2 O. The homogenization of the growth gel is carried out with stirring at 300 rpm for 25 minutes at 25.degree. Step 2): Introduction into the reaction medium of the structuring agent [0132] 27.3 g of 60% TPOAC solution in MeOH are introduced into the reaction medium with a stirring speed of 300 rpm. (TPOAC / A1203 molar ratio = 0.04). After 5 minutes of homogenization, the stirring speed is lowered to 50 rpm. Step 3): Ripening phase The stirred reaction medium is maintained at 50 rpm at 25 ° C for 22 hours and then the crystallization is started. Step 4): Crystallization 5 [0134] The stirring speed is maintained at 50 rpm and the set point of the jacket of the reactor is set at 80 ° C. so that the reaction medium rises to 75 ° C. C in 80 minutes. After 72 hours of residence at 75 ° C., the reaction medium is cooled by circulating cold water in the jacket to stop the crystallization. Step 5): Filtration / washing The solids are recovered on sinter and then washed with deionized water to neutral pH. Step 6): Drying / calcination In order to characterize the product, the drying is carried out in an oven at 90 ° C. for 8 hours, the loss on ignition of the dried product is 22% by weight. The calcination of the dried product necessary to release both the microporosity (water) and the mesoporosity by eliminating the structuring agent is carried out with the following temperature profile: 30 minutes of rise at 200 ° C., then 1 hour bearing at 200 ° C, then rising for 3 hours at 550 ° C, and finally 1.5 hours at 550 ° C. The microporous volume and the external surface measured according to the t-plot method 20 from the 77 K nitrogen adsorption isotherm after degassing under vacuum at 400 ° C. for 10 hours are respectively 0.260 cm3g. -1 and 90 m2.g-1. The number average diameter of the crystals of the mesoporous zeolite (or hierarchical porosity) thus obtained is 4.5 pm and the Si / Al ratio is equal to 1.24. In what follows a mass expressed in anhydrous equivalent means a mass of product less its loss on ignition. Example B2 Synthesis of zeolite crystals of LSXPH type of Si / Al = 1.01 ratio of external surface equal to 95 m 2 g -1 (according to the invention) a) Preparation of the growth gel: screw stirred reactor 'Archimedes at 30 250 rpm. In a 3-liter stainless steel reactor equipped with a heating jacket, a temperature probe and a stirrer, a growth gel is prepared by mixing an aluminate solution containing 300 g of sodium hydroxide. sodium (NaOH), 264 g of 85% potassium hydroxide, 169 g of alumina trihydrate (Al 2 O 3, 3H 2 O, containing 65.2% by weight of Al 2 O 3) and 1200 g of water at 25 ° C. in 5 minutes. with a stirring rate of 250 rpm with a silicate solution containing 490 g of sodium silicate, 29.4 g of NaOH and 470 g of water at 25 ° C. The stoichiometry of the growth gel is as follows: 4.32 Na 2 O / 1.85 K 2 O / Al 2 O 3 / 2.0 SiO 2/114 H 2 O. Homogenization of the growth gel is carried out with stirring at 250 rpm for 15 minutes at 25 ° C. b) Addition of the nucleation gel [0142] To the growth gel is added at 25 ° C. with stirring to 300 tr.min -1.11.6 g of nucleating gel (ie 0.4% by weight) of composition Na 2 O / Al 2 O 3/10 SiO 2/180 H 2 O prepared in the same manner as the growth gel, and matured for 1 hour at 40 ° C. After 5 minutes of homogenization at 250 rpm, the stirring speed is decreased to 50 rpm and continued for 30 minutes. c) Introduction into the reaction medium of the structuring agent [0143] 35.7 g of 60% TPOAC solution in methanol (MeOH) are introduced into the reaction medium with a stirring speed of 250 rpm. 1 for 5 minutes (ratio / molar TPOAC / Al 2 O 3 = 0.04). Then, at 30 ° C., a maturation step is carried out for 20 hours at 50 rpm to start the crystallization. d) Crystallization in 2 steps The stirring speed is maintained at 50 rpm and then an increase in the set point of the jacket of the reactor is set to 63 ° C. in a linear manner so that the reaction medium rises in temperature to 60 ° C in 5 hours followed by a plateau of 21 hours at 60 ° C; then set the setpoint of the jacket of the reactor at 102 ° C so that the reaction medium rises in temperature at 95 ° C in 60 minutes. After standing for 3 hours at 95 ° C., the reaction medium is cooled by circulating cold water in the jacket to stop the crystallization. E) Filtration / Washing The solids are recovered on sintered material and then washed with deionized water to neutral pH. f) Drying / Calcination [0146] In order to characterize the product, the drying is carried out in an oven at 90 ° C. for 8 hours. The calcination of the dried product necessary to release both the microporosity (water) and the mesoporosity by eliminating the structuring agent is carried out by vacuum degassing with a gradual increase in steps of 50 ° C. to 400 ° C. C for a period of between 9 hours and 16 hours under vacuum (P <6.7 × 10 -4 Pa). The microporous volume and the external surface measured by the t-plot method from the 77K nitrogen adsorption isotherm after vacuum degassing at 400 ° C for 10 hours are respectively 0.215 cm3g-1 and 95 m2.g-1. The average number diameter of the crystals is 6 μm. The diameters of the mesopores calculated from the nitrogen adsorption isotherm by the DFT method are between 5 nm and 10 nm. The RX diffractogram corresponds to a pure Faujasite (FAU) structure, no LTA zeolite is detected. The Si / Al molar ratio of the LSXPH determined by X-ray fluorescence is 1.01. Example B3: LSXPH zeolite crystal synthesis with an external surface equal to 146 m 2 g -1 (comparative example) A LSX zeolite with a hierarchical porosity of higher external surface area than the zeolite synthesized in Example B2 is obtained by strictly following the procedure of Example B2, except for the molar ratio TPOAC / Al 2 O 3 of Step 2 which is equal to 0.07. The microporous volume and the external surface measured by the t-plot method from the nitrogen adsorption isotherm at 77K after vacuum degassing at 400 ° C / 5 for 10 hours are 0.198 cm3, respectively. g-1 and 146 m2.g-1. The number average crystal diameter of the mesoporous zeolite (or hierarchically porous) thus obtained is 6 pm and the Si / Al ratio is 1.01. Example 1 (Comparative) Preparation of zeolite adsorbent in granular form with zeolite crystals of LSX according to Example A, 2.6 μm in diameter, and a kaolin type binder. An adsorbent is prepared by reproducing Example 6 described in Patent FR 2 925 366, and grains are recovered which are selected by sieving in the particle size range between 0.3 mm and 0.5 mm. , and such that the average volume diameter is 0.4 mm. The barium exchange rate of this adsorbent evaluated from the elemental chemical analysis by WDXRF is 97% and its loss on ignition is 6.2%. The mesh parameter measured by DRX on this adsorbent is evaluated at 25.19 ± 0.01 Å. The microporous volume and the external surface measured by the t-plot method from the nitrogen adsorption isotherm at 77K after vacuum degassing at 400 ° C for 10 hours are respectively 0.231 cm3g-1. and 7 m2.g-1. The total volume contained in the macropores and mesopores (sum of macroporous volume and mesoporous volume) measured by intrusion of mercury, is 0.25 cm3g-1. The ratio (macroporous volume) / (macroporous volume + mesoporous volume) is equal to 0.9. The mechanical strength of this adsorbent measured according to the method presented in the characterization techniques is 2.1 MPa. Example 2 (Comparative) Preparation of zeolitic adsorbent in pellet form with 4.5 μm size XPH crystals and a kaolin agglomeration binder such that the external surface is equal to 70 m 2 g -1 A homogeneous mixture consisting of 1600 g anhydrous equivalent of zeolite crystals X synthesized according to the procedure of Example B1 (crystal size 4.5 μm), 350 g of anhydrous equivalent of kaolin, 130 g is prepared. g of colloidal silica sold under the trade name Klebosol® 30 (containing 30% by weight of SiO2 and 0.5% of Na2O) as well as the amount of water which allows the agglomeration of the mixture by extrusion. The extrudates are dried, crushed to recover grains in the particle size range between 0.3 mm and 0.5 mm, and such that the average volume diameter is 0.4 mm, and then calcined for 2 hours at room temperature. 550 ° C under nitrogen sweep, then 2 hours at 550 ° C under dry decarbonated air sweep. The barium exchange is then operated with a concentration of barium chloride solution, BaCl 2, 0.7M at 95 ° C in 4 steps. At each stage, the ratio of volume of solution to mass of solid is 20 ml / g and the exchange is continued for 4 hours each time. Between each exchange, the solid is washed several times in order to rid it of excess salt. It is then dried at 80 ° C. for 2 hours and then activated at 250 ° C. for 2 hours under a stream of nitrogen. The barium exchange rate of this adsorbent evaluated from the elemental chemical analysis by WDXRF, as described above in the analytical techniques, is 97% and the loss on ignition is 5.5%. . The mesh parameter measured by DRX on this adsorbent is evaluated at 25.02 ± 0.01 Å. The microporous volume and the external surface measured according to the t-plot method from the nitrogen adsorption isotherm at 77K after vacuum degassing at 400 ° C. for 10 hours are 0.192 cm3g-1 and 70 respectively. m2.g-1. The total volume contained in the macropores and mesopores (sum of macroporous volume and mesoporous volume) measured by intrusion of mercury, is 0.33 cm3g-1. The ratio (macroporous volume) / (macroporous volume + mesoporous volume) is equal to 0.6. The mechanical strength of this adsorbent measured according to the method presented in the characterization techniques is 2.1 MPa, corresponding to the pressure necessary to obtain 0.5% of fines. EXAMPLE 3 (According to the Invention) Preparation of a zeolitic adsorbent in the form of granules with LSXPH crystals of size 6 μm and a kaolin-type agglomeration binder such that the external surface is equal to 64 m 2 [0158] An adsorbent is prepared in a manner identical to the preparation of the adsorbent of Example 2, but from LSX zeolite crystals synthesized according to the procedure of Example B2 (size of the crystals 6 pm). The barium exchange rate of this adsorbent evaluated from the elemental chemical analysis by WDXRF, as described above in the analytical techniques, is 97% and the loss on ignition is 5.0%. . The mesh parameter measured by DRX on this adsorbent is evaluated at 25.20 ± 0.01 Å. The microporous volume and the external surface measured according to the t-plot method from the nitrogen adsorption isotherm at 77K after vacuum degassing at 400 ° C. for 10 hours are 0.167 cm3g-1 and 64 respectively. m2.g-1. The total volume contained in the macropores and mesopores (sum of macroporous volume and mesoporous volume) measured by mercury intrusion is 0.29 cm3g-1. The ratio (macroporous volume) / (macroporous volume + mesoporous volume) is equal to 0.73. The mechanical strength of this adsorbent measured according to the method presented in the characterization techniques is 2.3 MPa, corresponding to the pressure necessary to obtain 0.5% of fines. Example 4 (Comparative) Preparation of zeolite adsorbent in granular form with 6 μm thick LSXPH crystals and a kaolin agglomeration binder such that the external surface is 121 m 2 g-1 [0162] An adsorbent is prepared in a manner identical to the preparation of the adsorbent of Example 3, but from LSX zeolite crystals synthesized according to the procedure of Example B3 (average number of crystals of the crystal 6 μm). The barium exchange rate of this adsorbent evaluated from the elemental chemical analysis by WDXRF, as described above in the analytical techniques, is 97% and the loss on ignition is 5.1%. . The mesh parameter measured by DRX on this adsorbent is evaluated at 25.21 ± 0.01 Å. The microporous volume and the external surface area measured by the t-plot method from the 77K nitrogen adsorption isotherm after vacuum degassing at 400 ° C. for 10 hours are 0.147 cm 3, respectively. g-1 and 121 m2.g-1. The total volume contained in the macropores and mesopores (sum of macroporous volume and mesoporous volume) measured by mercury intrusion, is 0.34 cm3g-1. The ratio (macroporous volume) / (macroporous volume + mesoporous volume) is equal to 0.63. The mechanical strength of this adsorbent measured according to the method presented in the characterization techniques is 2.2 MPa, corresponding to the pressure necessary to obtain 0.5% of fines. EXAMPLE 5 [0166] A piercing test (frontal chromatography) is carried out on the adsorbent of Example 2 and on the adsorbent of Example 3 according to the invention to evaluate their selectivity for the adsorption of paraxylene with respect to ethylbenzene. The amount of adsorbent used for this test is about 34 g. The procedure for obtaining the drilling curves is as follows: 15 - filling of the column with the adsorbent and setting up in the test bench; filling with the desorption solvent at room temperature; progressive rise at 175 ° C. under a flow of solvent (5 cm 3 min -1); injection of solvent at 5 cm.sup.-3 min when the adsorption temperature (175.degree. C.) is reached; Solvent / charge permutation to inject the charge (5 cm 3 min -1); - collection and analysis of the drilling effluent; the injection of the charge will be maintained until the solvent concentration in the effluent is zero. The desorption solvent used is para-diethylbenzene. The selectivity between two isomers is evaluated using a feed containing 45% by weight of each of the 25 isomers and 10% by weight of a tracer (isooctane) used for the estimation of the non-selective volumes and not involved in the process. separation. The test carried out uses a filler whose composition of the filler is the following: - Paraxylene: 45% by weight, - Ethylbenzene: 45% by weight, 30 - Iso-octane: 10% by weight [0169] The pressure is sufficient for the charge remains in the liquid phase at the adsorption temperature, ie 1 MPa. The superficial velocity is 0.2 cm.s-1. The selectivity of paraxylene with respect to ethylbenzene is calculated from the adsorbed quantities of each compound, the latter being determined by material balance from the first moments of the drilling curves of all the compounds. constituents present in the effluent. The results are shown in Table 1 below: Table 1 - Example Adsorption capacity Total selectivity of xylenes (cm3.g-1) PX / EB Adsorbent of Example 2 (comparative) 0.178 2.06 Adsorbent of Example 3 (Invention) 0.181 2.53 Adsorbent of Example 4 (comparative) 0.183 1.95 In the table above: the adsorption capacity of xylenes is expressed in cm 3 of C8-aromatics adsorbed per gram of adsorbent; "PX" means paraxylene and "EB" means ethylbenzene [0172] The adsorbents of Examples 2 to 4 have comparable total adsorption capacities for xylenes. On the other hand, the adsorbent of Example 3, according to the invention, has a selectivity between para-xylene and ethylbenzene of greater than 2.5 while the selectivity obtained with the adsorbents of Examples 2 and 4 is less than 2.1. The adsorbent of Example 3 will therefore be more efficient in separating a feed rich in ethylbenzene.
[0005] Example 6: [0173] The purpose of Example 6 is to illustrate the productivity gain obtained with an adsorbent according to the invention (adsorbent of Example 3) with respect to: an adsorbent with LSX zeolite crystals non-compliant outer surface (too weak) according to the prior art (comparative adsorbent of Example 1), and a non-compliant outer surface adsorbent (too high) with LSX zeolite crystals of Si / Si ratio. Al equal to 1.00 ± 0.05 (adsorbent of Example 4). The adsorbents of Examples 1, 3 and 4 were tested to evaluate their performance in separating paraxylene on a simulated countercurrent chromatography pilot unit consisting of 15 columns in series of 2 cm in diameter, of 1.10. m of length. The circulation between the last and the first column is done by means of a recycling pump. At each intercolumn link, one can inject either a charge to be separated or desorbent. You can also extract either a raffinate or an extract. All columns and dispensing winnowing is maintained at 175 ° C, and the pressure is maintained above 1.5 MPa. The offsets of the different injection or withdrawal points are simultaneous according to a permutation time that can be adjusted. The beds are divided into four chromatographic zones according to the following configuration: - 3 beds between the desorbent injection and extract withdrawal defining the zone 1-6 beds between the extraction of extract and the injection of charge defining the zone 2 - 4 beds between the charge injection and the raffinate withdrawal defining the zone 3 - 2 beds between the raffinate withdrawal and the desorbent injection defining the zone 4. [0175] The charge is composed 21.3% by weight of paraxylene, 19.6% of orthoxylene, 45.1% of metaxylene and 14.0% of ethylbenzene. In a first step, a test is carried out from the adsorbent according to Example 1. This test makes it possible to determine the charge injection and desorbent flow rates necessary to obtain paraxylene with a purity of 99. 7% and a yield of at least 97%. The paraxylene is obtained at the extract at a purity of 99.7% and a yield of 97% by injecting the feedstock at a flow rate of 39.5 g.min-1 and the desorbent at a flow rate of 35.degree. 5 g.min-1, and applying a time of switching injection points and racking 118 seconds. The extract rate is 24.7 grams per minute and the zone flow rate is 105.9 grams per minute. Subsequently, all of the adsorbents are tested by applying the same desorbent flow rate. On the other hand, the charge flow, the time of rotation of the injection and withdrawal points, as well as the recycling flow rate can be adjusted in order to reach the required performances, namely a purity of 99.7% and a yield of 97%. The results are reported in Table 2. - Table 2 - Adsorbent Example 1 Example 3 Example 4 (comparative) (according to the invention) (comparative) External surface (m2.g-1) 7 64 121 Column length (m ) 1,1 1,1 1,1 permutation time (s) 118 66 65 Desorbent flow rate (g.min-1) 35,5 35,5 35,5 Extracted flow rate (g.min-1) 24,7 19 , 9 19.5 Flow rate zone 4 (g.min-1) 105.9 194.8 197.7 Purity 99.70% 99.70% 99.70% Yield 97.00% 97.00% 97.00% Charge rate (g.min-1) 39.5 49.9 28.5 3028430 - 3 - Figure 3 illustrates the variation of the charge flow as a function of the external surface, the 3 points corresponding to examples 1, 3 and 4 of Table 2. Using LSX crystal adsorbent beads having an external surface area of 64 m 2 g -1, that is, adsorbents according to the invention, it is It is possible to obtain a paraxylene with the required purity and yield performance by injecting a higher feed rate than that treated with the ex-adsorbent. Reference Example 1, while injecting the reference desorbent flow rate, namely 35.5 g.min-1, using identical columns. For example, with the adsorbent of Example 3 according to the invention, it is possible to produce paraxylene at a purity of 99.7% with a yield of 97% identical to those obtained with the adsorbent of the invention. Reference Example 1 while increasing the load rate by 26%. Therefore, at iso-specification, the productivity is increased by 26% with the adsorbent of Example 3 according to the invention relative to the adsorbent of Example 1. [0182] In contrast to the adsorbents according to the invention, using adsorbent beads based on LSX crystals having an external surface greater than 100 m 2 g -1, that is to say beyond the upper limit defined by the invention, it is not possible to obtain a paraxylene with the required purity and yield performance by injecting a feed rate greater than or equal to that treated with the adsorbent of Reference Example 1, while injecting the reference desorbent flow rate, i.e. 35.5 g.min-1, using identical columns. On the contrary, to obtain the required purity and yield performance with surface surface adsorbents at 100 m 2 g -1, a lower feed rate than that treated with the adsorbent of Reference Example 1 will be treated. [0183] For example, with the adsorbent of Example 4 based on LSX crystals with an external surface equal to 121 m2.g-1, that is to say differing from the invention by an external surface greater than 100 m 2 g -1, can produce paraxylene at a purity of 99.7% with a yield of 97% identical to those obtained with the adsorbent of Example 1 reference while decreasing the flow rate of charge 28%. Therefore, at iso-specification, the productivity is decreased by 28% with the adsorbent of Example 4 relative to the adsorbent of Example 1. Example 7: [0184] The purpose of Example 7 is to to illustrate the productivity gain obtained with an adsorbent according to the invention (adsorbent of Example 3) with respect to an adsorbent having the same external surface, but with crystals of zeolite X (adsorbent of the invention). Example 2), for charges containing ethylbenzene. The adsorbents of Examples 2 and 3 were tested to evaluate their performance in separating paraxylene on a simulated countercurrent chromatography pilot unit consisting of 15 columns in series of 2 cm in diameter, 1.10 m in diameter. length according to a functioning identical to that described in example 6. [0186] Three charge compositions are used to evaluate the impact of the ethylbenzene content thereon on the productivity of the adsorbents: a charge composed of 21, 3% by weight of paraxylene, 19.6% of orthoxylene, 45.1% of metaxylene and 14.0% of ethylbenzene by mass, as in the previous example, - a compound charge of 21.3 % by weight of paraxylene, 23.8% of orthoxylene and 54.9% of metaxylene, filler not containing ethylbenzene, - a filler composed of 21.3% of paraxylene, 14.8% of orthoxylene, 33.9% metaxylene and 30% ethylbenzene by mass. In Example 6, a test was carried out from the adsorbent of Example 3 according to the invention. This test made it possible to determine the charge and desorbent injection rates necessary to obtain paraxylene with a purity of 99.7% and a yield of at least 97%, for the feed containing 14% of ethylbenzene. The paraxylene in the extract is obtained at a purity of 99.7% and a yield of 97% by injecting the feedstock at a flow rate of 49.9 g / minute and the desorbent at a rate of 35.degree. 5 g.min-1, and applying a time of rotation of the injection points and withdrawal of 66 seconds. The extract rate is 19.9 g.min-let the zone 4 flow rate is 194.8 g.min-1. [0189] Subsequently, the adsorbents of Example 2 and Example 3 are tested with the different fillers by applying the same desorbent flow rate. On the other hand, the charge flow, the time of rotation of the injection and withdrawal points, as well as the recycling flow rate can be adjusted in order to reach the required performances, namely a purity of 99.7% and a yield of 97%. The results are reported in the following Table 3: Table 3 - Change in the composition of the load:% EB Adsorbent based Adsorbent based Adsorbent based Adsorbent based Adsorbent with Adsorbent based on crystals X crystals LSX- crystals X- crystals LSX-based crystal crystals LSX- Example Example 2 Example 3 Example 2 Example 3 X- Example 2 Example 3 (comparative) (according to the invention) (comparative) (according to the invention) (comparative) (according to the invention) External surface (m2.g-1) 70 64 70 64 70 64 Ethylbenzene content in the filler (% mass) 0% 0% 14% 14% 30% 30% Length column (m) 1,1 1,1 1,1 1,1 1,1 1,1 permutation time (s) 66 66 66 66 66 66 Desorbent flow rate (g.miril) 35.5 35.5 35.5 35 , 35.5 35.5 Flow rate extracted (g.mirfl) 19.9 19.9 21.8 19.9 19.0 19.8 Flow rate Zone 4 (g.min-1) 194.6 194.6 194 , 8 194.8 195.0 194.9 Purity = 99.70% 99.70% 99.70% 99.70% 99.70% 99.70% Yield = 97.00% 97.00% 97.00 % 97.00% 97.00% 97.00% Charge rate (g.mi n-1) 50.7 50.7 47.8 49.9 44.6 48.7 w O op w O 3028430 36 [0190] Figure 4 illustrates the variation of the charge flow as a function of the content of ethylbenzene contained in this, in the case of the adsorbent according to Example 2, based on X crystals and in the case of the adsorbent according to Example 3 according to the invention based on LSX crystals. In this example, using the adsorbent of Example 3 according to the invention, it is possible to obtain a paraxylene with the required performance of purity and yield, by injecting a charge flow greater than or equal to that treated with the adsorbent of Comparative Example 2, while injecting the reference desorbent flow rate, namely 35.5 g.min-1, using identical columns, regardless of the ethylbenzene content obtained in FIG. charge. It is also observed that the productivity gain provided by the adsorbent of Example 3 according to the invention is all the greater as the ethylbenzene content is high. There is also less variability in productivity as a function of the ethylbenzene content in the case of the adsorbent of Example 3 compared with the adsorbent of Example 2. For a charge composition varying between 0 and 30% in ethylbenzene, there is a productivity variation of less than 5% in the case of the adsorbent of Example 3 according to the invention. On the contrary, for the same variation in composition, there is a productivity variation of greater than 12% in the case of the adsorbent of Example 2 according to the invention.

权利要求:
Claims (15)
[0001]
REVENDICATIONS1. A zeolitic adsorbent comprising at least one zeolite of FAU structure of the LSX type, comprising barium and / or potassium, and for which the external surface of said zeolite adsorbent, measured by nitrogen adsorption, is between 20 m 2 g -1 and 100 m2.g-1, and preferably between 20 m2.g-1 and 80 m2.g-1 and more preferably between 30 and 80 m2.g-1 limits included.
[0002]
2. The zeolite adsorbent according to claim 1, in which the zeolite with structure FAU is a zeolite of structure FAU of type LSX for which the number average diameter of the crystals is between 0.5 μm and 20 μm, limits included, preferably between 0.5 μm and 10 μm, limits included, more preferably between 0.8 μm and 10 μm, limits included, more preferably between 1 μm and 10 μm, limits included, and more preferably between 1 μm and 8 μm, terminals included.
[0003]
A zeolite adsorbent according to claim 1 or 2, wherein the barium content (Ba) expressed as barium oxide (BaO) is greater than 25%, preferably greater than 28%, very preferably greater than 34%, even more preferably greater than 37%, by weight relative to the total weight of the adsorbent.
[0004]
4. Zeolitic adsorbent according to one of the preceding claims, wherein the potassium content (K), expressed as potassium oxide (K20), is less than 30%, preferably less than 15% and preferably between 0 % and 10%, limits included by weight relative to the total weight of the adsorbent.
[0005]
5. zeolite adsorbent according to one of the preceding claims, wherein the total volume contained in the macropores and mesopores measured by mercury intrusion, is between 0.15 cm3.g-1 and 0.5 cm3.g-1 preferably between 0.20 cm3g-1 and 0.40 cm3g-1 and very preferably between 0.20 cm3g-1 and 0.35 cm3g-1, inclusive.
[0006]
6. Zeolitic adsorbent according to any one of the preceding claims, wherein the mass fraction of zeolite FAU is greater than or equal to 85%, preferably greater than or equal to 90% by weight relative to the total weight of the adsorbent. 3028430 38
[0007]
7. Zeolitic adsorbent according to any one of the preceding claims, having a ratio (macroporous volume) / (macroporous volume + mesoporous volume) of between 0.2 and 1, very preferably between 0.5 and 0.9, terminals included.
[0008]
8. Process for the preparation of a zeolite adsorbent according to any one of the preceding claims, said process comprising at least the steps of: a) agglomeration of crystals of at least one zeolite of structure FAU LSX type having an external surface between 20 m 2 g -1 and 150 m 2 g -1, inclusive, the number-average diameter of the crystals of which is between 0.5 pm and 20 pm inclusive, with a binder preferably comprising at least 80 % of clay or a mixture of clays and up to 5% of additives as well as with the quantity of water which allows shaping of the agglomerated material, then drying and calcination of the agglomerates; b) optionally zeolizing step of all or part of the binder by contacting the agglomerates obtained in step a) with an aqueous basic solution; c) cationic exchange (s) of the agglomerates of step b) by contacting with a solution of barium ions and / or potassium ions; d) additional cationic exchange of the agglomerates of step c) by contacting with a solution of potassium ions; e) washing and drying the agglomerates obtained in steps c) or d), at a temperature between 50 ° C and 150 ° C; and f) obtaining the zeolite adsorbent according to the invention by activating the agglomerates obtained in step e) under oxidizing and / or inert gaseous flushing, with in particular gases such as oxygen, nitrogen, air , a dry air and / or decarbonated oxygen-depleted air, optionally dry and / or decarbonated, at a temperature between 100 ° C and 400 ° C, preferably between 200 ° C and 300 ° C.
[0009]
9. Process according to claim 8, in which the clays are preferably chosen from: kaolin, kaolinite, nacrite, dickite, halloysites, attapulgite, sepiolite, montmorillonite, bentonite, illite and metakaolin, as well as mixtures of two or more of between them in all proportions.
[0010]
10. Use of a zeolitic adsorbent according to any one of claims 1 to 7 or prepared according to one of claims 8 to 9, as adsorption agent in: - the separation of cuts of aromatic isomers C8 and in particular xylenes, - the separation of isomers of substituted toluene such as nitrotoluene, diethyltoluene, toluenediamine, and others, - the separation of cresols, - the separation of polyhydric alcohols, such as sugars.
[0011]
11. Process for separating the isomers of xylenes in the gas phase or in the liquid phase employing at least one zeolite adsorbent according to any one of claims 1 to 7 or prepared according to one of claims 8 to 9.
[0012]
12. Separation process according to claim 11, which is a process for separating paraxylene from a filler of cuts of aromatic isomers with 8 carbon atoms, using, as paraxylene adsorption agent, a zeolite adsorbent according to US Pat. any one of claims 1 to 7 or prepared according to one of claims 8 to 9.
[0013]
13. The method of claim 12, implemented in a simulated moving bed adsorption industrial unit, operating against the current under the operating conditions: - number of beds: 4 to 24; - number of zones: at least 4 operating zones, each located between a feed point and a draw point; temperature between 100 ° C and 250 ° C; pressure between the bubble pressure of xylenes (or toluene when toluene is chosen as the desorbent) at the process temperature and 3 MPa; - Desorbent flow rate report on charge to be treated: 0.7 to 2.5; recycling rate: 2 to 12, preferably 2.5 to 6; - Cycle time, corresponding to the time between two injections of desorbent on a given bed: between 4 and 25 min.
[0014]
The process of claim 13, wherein the desorbent is toluene or paradiethylbenzene.
[0015]
The method of any one of claims 13 or 14, wherein the water content in the incoming streams is adjusted between 20 ppm and 150 ppm.

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2017-10-27| TP| Transmission of property|Owner name: IFP ENERGIES NOUVELLES, FR Effective date: 20170922 Owner name: ARKEMA FRANCE, FR Effective date: 20170922 |

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优先权:

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申请号 | 申请日 | 专利标题

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FR1460953A|FR3028430B1|2014-11-13|2014-11-13|LSX ZEOLITHIC ZEOLITHIC ADSORBENTS WITH EXTERNAL SURFACE CONTROL, PREPARATION METHOD AND USES THEREOF|

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FR1460953|2014-11-13|FR1460953A| FR3028430B1|2014-11-13|2014-11-13|LSX ZEOLITHIC ZEOLITHIC ADSORBENTS WITH EXTERNAL SURFACE CONTROL, PREPARATION METHOD AND USES THEREOF|

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CN202011122763.5A| CN113083224A|2014-11-13|2015-11-13|Zeolitic adsorbents made of LSX zeolite with controlled external surface area, method for preparing same and uses thereof|

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JP2017525937A| JP6641368B2|2014-11-13|2015-11-13|Zeolite-based adsorbent material containing LSX zeolite as a main component with controlled outer surface area, method for preparing zeolite-based adsorbent material, and use of zeolite-based adsorbent material|

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US15/526,130| US9919289B2|2014-11-13|2015-11-13|Zeolite-based adsorbents based on LSX zeolite of controlled outer surface area, process for preparing them and uses thereof|

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EP15797924.6A| EP3218101A1|2014-11-13|2015-11-13|Zeolite adsorbents made from lsx zeolite with a controlled external surface area, method for preparation of same and uses thereof|

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TW104137610A| TWI598149B|2014-11-13|2015-11-13|Zeolite-based adsorbents based on lsx zeolite of controlled outer surface area, process for preparing them and uses thereof|

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PCT/EP2015/076532| WO2016075281A1|2014-11-13|2015-11-13|Zeolite adsorbents made from lsx zeolite with a controlled external surface area, method for preparation of same and uses thereof|

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KR1020177015924A| KR20170083602A|2014-11-13|2015-11-13|Zeolite adsorbents made from lsx zeolite with a controlled external surface area, method for preparation of same and uses thereof|

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CN201580061489.6A| CN107206349B|2014-11-13|2015-11-13|Zeolitic adsorbents made of LSX zeolite with controlled external surface area, method for preparing same and uses thereof|

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ZA2017/03816A| ZA201703816B|2014-11-13|2017-06-02|Zeolite adsorbents made from lsx zeolite with a controlled external surface area, method for preparation of same and uses thereof|